If you think the term "app store" has already appeared in more than enough places, brace yourself. Hewlett-Packard has just applied the concept to an area it claims is as-yet-untouched territory: the SDN market.

At its core, HP's idea isn't complicated. The company has created what it describes as an "open ecosystem" for its OpenFlow-based SDN products, although these days the definition of "open" varies depending on who you talk to. In this case, it's open in the sense of being based on OpenFlow and anyone can participate: Developers can grab an SDK and create apps that make use of HP SDNs and support services in this open ecosystem.

The most interesting part of the idea is the app store. Those who have created apps for HP's SDNs can place the apps in HP's SDN App Store and re-sell them. Likewise, HP SDN users can browse the app store and download and purchase apps for their own SDN. The SDK is free, although you need to pay $495 for a controller to test out your SDN apps in HP's SDN Virtual Lab and simulation suite. (HP AllianceOne partners can get the controller at a 55 percent discount.)

It's a clever idea, and it further points up how one of the initial problems of most any software ecosystem is not just a lack of curation, but discovery. Apple's "walled garden" app store model may have been derided by any number of folks who resented the idea of only being allowed to use a certain predetermined set of apps, but it created a model that many others have followed. Linux repositories allow a set of known-good software to be made readily available to a given distribution, but it's often bewildering to sift through them and figure out what works best for what.

HP's SDN App Store, then, looks like an attempt to mix two metaphors: the closed-ended curation -- and monetization models -- of the consumer app stores, and the freedom of an open software ecosystem. Those who know what they want in their SDN can go get (or develop) it on their own, while those who need guidance can turn to the app store to shop for a solution provided by a name vendor. Microsoft, Intel, SAP, VMware, and Citrix have all signed on, and a number of as-yet-unannounced apps by various partners will be unveiled shortly.

Conspicuously absent from the vendor and partner list is Cisco, of course, who is No. 1 in the networking space to HP's very distant second. Despite an endless barrage of attempts to undermine its business -- e.g., Cumulus Linux or the products in Juniper Network's lineup -- Cisco has remained firmly seated and has its own plans for how to make SDNs a cornerstone of its business. Cisco's Insieme architecture devices are scheduled to hit the market this fall, and the company recently announced its own Internet-of-everything routing hardware.

But there's little talk from Cisco about OpenFlow or other such initiatives -- and for good reason: The company has consistently disdained OpenFlow and has instead thrown its weight behind another SDN framework, the OpenDaylight collaboration with IBM and others. Something like HP's SDN App Store could create a far broader arena of useful apps for enterprise customers -- and enterprising developers.

Let's see how Cisco plans to respond to competition that not only offers an already recognized open ecosystem, but also provides those who use it with a way to monetize their participation.